1. Field of the Invention
The present invention relates to a method of forming bumps and a bonding tool for forming bumps, a semiconductor wafer, a semiconductor chip and a semiconductor device, and methods of fabrication thereof, a circuit board and an electronic instrument.
2. Description of the Related Art
Methods of forming a bump on an electrode of a semiconductor chip using wire bonding technology are well known. For example, Japanese Patent Application Laid-Open No. 57-163919 discloses a method in which a wire is bonded to an electrode by a capillary, and the wire is then torn off so that a fragment of the wire remains on the electrode to form a bump. This method is able to form a bump more rapidly than by cumulative plating.
However, a bump formed by tearing off a wire does not adequately assure a flat upper surface, and therefore while no problems occur when using face-down bonding of a semiconductor chip on a substrate, when bonding a lead to a bump there is a problem of inferior junction accuracy. That is to say, since an upper surface of the bump is jagged or has very little surface area that is flat, the bonding area with the lead is insufficient, and the lead tends to slip off the bump.